nace. As the flame goes onward to the flue end, it finds colder and colder blooms and gives up its heat, so that if we conceive a furnace of indefinite length, the escaping gases will be entirely cold. .
One of the difficulties about a continuous furnace is to move the pieces from one end to the other. The natural and almost universal way is to put the hearth on an angle, but some power must be applied. In Europe, where such furnaces are common, it is not unusual to roll the blooms or ingots forward by hand labor, but the cost of such labor would be prohibitive in America, while this practice gives rise to heavy loss, as the coating of scale falls off at every turn and exposes a fresh surface to oxidation. It is impossible to say how much of the heavy oxidation in some foreign works is due to this cause and how much to a sharper flame than is customary in America. Rails are sometimes buried in the hearth of the fur-r nace, which are replaced when they burn away, the ingots being pushed forward by power; in other cases, no rails are used, but the ingots are simply pushed along the sand bottom, which is much torn by the operation.
In America the general practice is to have the billets rest on. water-cooled pipes. These pipes absorb considerable heat and cool the under side of the bloom somewhat, but the gain in time and labor covers this small loss. Such furnaces in this country, with few exceptions, are used for billets not over 6 inches square, since it is difficult to heat larger blooms uniformly on the top and bottom, and there is not time when they reach the end of the furnace to turn them over and let the under side get hot. In the exceptions just noted, the blooms are of uniform size and the conditions are favorable, a furnace of this type being successfully operated on pieces 8 inches sqtiare and 1.0 feet long. The continuous furnace saves little fuel, for it does not produce steam like a reverberatory furnace, but it saves considerable in furnace labor..
SEC. IXe.—Coke, ovens.—Almost all the coke of America and about three-fourths of that produced in England is made in beehive ovens, whereby a pile of coal is burned slowly until the volatile matters are expelled, these volatile matters passing away in clouds of smoke. This smoke is a rich gas during the early stages of the operation, and might be used as a source of heat if such plants were in the neighborhood of industrial establishments. In . Belgium and Germany bee-hive ovens were long since superseded by